Three-phase magnetic core



July 25, 1950 J. J. VIE'N'NEAU mas-ms nan-mm coax 2 Sheets-Sheet 1 Filed Jan. 18, 1947 Patented July 25, 1950 2,516,164 THREE-PHASE MAGNETIC CORE Jacob J. Vienneau, Pittsfleld, Mass., assignor to General Electric Company, a corporation of New York Application January 18, 1947, Serial No. 722,849

1 Claim. 1

This invention relates to magnetic cores, particularly three phase cores for induction apparatus and more particularly to a method of making such cores and assembling such apparatus.

These cores are characterized by a compact design which is suitable for economical use in circular cross section transformer tanks and they also utilize to good advantage the grain direction of magnetic materials having a most favorable magnetic direction corresponding to the grain direction. An example of such material is high reduction, cold rolled silicon strip steel.

An object of the invention is to provide a new and improved magnetic core.

-Another object of the invention is to provide a novel and compact three phase magnetic core for stationary induction apparatus.

A further object of the invention is to provide a novel method of making magnetic cores and assembling induction apparatus. Claims to that subject matter have been presented in a divisionai application, Serial Number 93,072, filed May 13, 1949, and assigned to the same assignee.

The invention will be better understood from the following description taken in connection with the accompanying drawings and its scope will be pointed out in the appended claim.

In the drawings, Fig. 1 is a perspective view of an embodiment of the invention; Fig. 2 is a perspective view, during an intermediate stage of construction, of one of the yoke members used in Fig. i; Fig. 3 is a perspective View of a yoke member in another stage of its manufac ture; Fig. l is a detail view showing the method of assembling the core shown in Fig. 1; Fig. 5 is a perspective view of a modified core construc tion; Fig. 6 is a view of one of the parts of the modification shown in Fig. 5 during an intermediate stage of the construction; Fig. 7 is a detail view showing how the part of Fig. 6 is ,cut into generall two-turn length pieces, and

Fig. 8 is a perspective view of another part of the core shown in Fig. 5.

Referring now to the drawing and more particularly to Fig. l, the core comprises three straight legs i, 2 and 3 whose corresponding ends are joined by generally circular yokes 4 and 5.

The yokes are formed by winding a long strip of suitable material, such as high reduction cold rolled silicon steel, into a multi-turn spiral. As shown in Fig. 2, comparatively short spacers 6 are placed between the turns at three symmetrically spaced locations which are separated by The outer end of the strip which forms the yoke is fastened in any suitable manner such as by tack welds which are indicated at I. The portions of the yoke spiral which contain the spacers are clamped tightly so as to make three flat or straight portions on the yoke While the yoke is being strain relief annealed. After the yoke has been annealed, the strip may be cut as at 8 in Fig. 2 so as to loosen the turns and permit easy removal of the inserted spacers 6. The yoke with the spacers removed looks like the upper part of Fig. 3 in which it will be seen that spacers between the laminations are provided for receiving straight leg laminations. However, for facilitating assembly of the second yoke (it may be either the upper or lower yoke) with the leg laminations it is preferable to unwind it and cut it into convenient lengths of one or two urns. One of these but portions is indicated at 9 in Fig. 3.

The core is preferably assembled by placing an uncut yoke with the spacers removed on a flat surface and inserting the leg laminations in the spaces provided therefor in the yoke. As will be seen in Fig. alternate leg laminations extend into the spaces between the yoke laminations and the intermediate leg laminations butt up against the edge of the intermediate yoke laminations. The legs are shown by way of example as having a stepped or cruciform cross section. After the straight leg iaminations are assembled with one of the yokes, windings such as are indicated by til, it and S2 in Fig. l are slid onto the respective legs. The second yoke is then put into place preferably by building it up from the relatively short length pieces which have been cut from the wound yoke. This makes it much easier to insert the yoke laminations between the ends of the leg laminations. However, it is not essential that the second yoke be cut into short length pieces and it can with sufficient care be fitted into place with the ends of the leg laminations inserted in the proper spaces. In the modification shown in Fig. 5, there is a wound magnetic loop having opposite leg portions l3 and i4 combined with a U-shaped member 15. The leg portions l3 and I4 carry windings I6 and I8 and the central portion of the U-shaped member l5 constitutes a leg portion on which is mounted winding ll. The loop having the legs l3 and I4 is formed by winding 8. sumciently long strip of magnetic material on a suitably shaped mandrel to form the rectangular laminated structure shown in Fig. 6. Spacers I9 are inserted between the turns at opposite ends. The finished loop may be held together by retaining band 20 and the loop is then given a strain relief anneal at the-proper temperature and under the proper atmospheric conditions.

After it has been annealed, the loop shown in Fig. 6 is unwound and cut into lengths of any suitable number of turns such as two turns. Two of these two-tum cut loops are shown at 2| and 22 in Fig. 7.

The member I5 is made by cutting a loop of the type shown in Fig. 6 in half through the center of the inserts I9 after the loop has been annealed. This will result in two members each of which looks like the part shown in Fig. 8 because after the loop has been cut in half, the half spacers between the ends will drop out.

The core shown in Fig. 5 is assembled by lacing or threading the cut pieces which form the loop having legs I3 and I4 through the coils I6 and I8. The parts are threaded through one at a time with their ends brought into contact so that they occupy the same relative positions they did before they were cut. In this manner, the loop has its legs I3 and I4 provided with windings I6 and I8.

The member I5 is inserted in the winding I! by lacing or threading its individual laminations through the window of the winding I'I, one piece at a time, until the member I5 is built up to the proper height. The pieces are put through in the same order and occupy the same relative positions that they did when the member I5 was formed originally. The spaced ends of the member I5 are then fitted into the spaces which had previously been occupied by the spacers I9 so as to provide a low reluctance magnetic joint.

While there have been shown and described particular embodiments of the invention, it will be obvious to those skilled in the art that changes and modifications can be made without departing from the invention and therefore it is aimed in the appended claim to cover all such changes and modifications as fall within the true spirit andscope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

A three phase magnetic core comprising. in combination, a pair of generally hexagonal shaped yoke members, each of said members comprising a plurality of radially nested turns of flatwise curved magnetic strip material, the turns in three symmetrically spaced sides of said hexagonally shaped members being straight and radially separated, said yoke members being coaxially spaced from each other, one of said yoke members being a continuous strip of magnetic material, the other of said yoke members being a series of nested end to end related relatively short strips of magnetic material of the order of one to two turns in length, and three similar leg members each comprising a plurality of straight I fiat contiguous laminations of magnetic strip material, alternate leg laminations having their ends extending beyond the ends of the intermediate leg laminations, said leg members interconnecting said yoke members with the ends of the alternate leg laminations fitting into the spaces between the separated straight portions of the yoke turns.

JACOB J.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

